The invention relates to rotary disc- or wheel-shaped parts in general, and more particularly to improvements in rotary parts which can perform the function of, or can be used in conjunction with, driving or idler pulleys. For the sake of convenience and simplicity, the rotary parts to which the present invention pertains will be called sheaves.
German patent application No. 34 02 001 A1 of Bannasch et al. (published Jun. 30, 1985) discloses a pulley wherein a grooved rim is connected to a hub by a damper consisting of a relatively thick rubber disc. A drawback of such pulleys is that their useful life is rather short because the material of the disc is affected by heat and by the developing torque. Furthermore, the extent of angular displacement of the rim and hub relative to each other is rather small because the so-called spring rate or spring gradient is relatively small and, therefore, an operation within the critical range is unavoidable. In addition, pronounced internal friction of the material of the disc entails that the insulating effect within the supercritical range is relatively decoupling. This, in turn, renders it necessary to employ a relatively large V-belt as well to resort to complex and expensive belt tensioning devices. The belt must be tensioned with a considerable force, and the space requirements of the pulley (particularly in axial direction) are quite pronounced. The situation is analogous if the rubber disc is Bannasch et al. is built into a so-called inertial damper. Heretofore known inertial dampers are rotated by a shaft or by another driving member without the interposition of an antifriction bearing between their input and output elements.